MODEL PAPER 9 Science - MODEL PAPER 9

Assertion (A): The energy which passes to the herbivores does not come back to autotrophs. .
Reason (R): The flow of energy in a food chain is unidirectional.

Assertion (A): Sexual reproduction increases genetic diversities and plays a role in origin of new species.
Reason (R): Sexual reproduction involves the formation of gametes and fusion of gametes.

Assertion (A): Copper spoon is used to stir silver nitrate solution.
Reason (R): Copper is less reactive than silver

Which of the following are environment-friendly practices?

Assertion (A): Copper spoon is used to stir silver nitrate solution.
Reason (R): Copper is less reactive than silver

Assertion (A): Sexual reproduction increases genetic diversities and plays a role in origin of new species.
Reason (R): Sexual reproduction involves the formation of gametes and fusion of gametes.

Assertion (A): The energy which passes to the herbivores does not come back to autotrophs. .
Reason (R): The flow of energy in a food chain is unidirectional.

Is the position of a star as seen by us its true position? Justify your answer.

What are the characteristics of energy transfer in biosphere?

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Discuss the major steps involved in process of nutrition in human beings.

A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine? Support your answer with reasons.

A pea plant with purple flowers were crossed with white flowers producing 40 plants with only purple flowers. On selfing, these plants produced 470 plants with purple flowers and 162 with white flowers. What genetic mechanism account for these results.

Describe the alimentary canal of man.

Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.
i. State the nature of the lens and the reason for its use.
ii. Where should the palmist place/hold the lens so as to have a real and magnified image of an object?
iii. If the focal length of this lens is 10 cm and the lens is held at a distance of 5 cm from the palm, use lens formula to find the position and size of the image.

Given below is a labelled diagram of the human brain.



Using the given diagram, answer the following questions:
i. Which part of the brain controls reflex movements of the head, neck, and trunk?
ii. Name the part of the human brain which contains a vital centre for controlling blood pressure.
iii. Which part of the hindbrain regulates respiration?
iv. How is the brain protected from injuries and shock?
v. Which part of the human brain is the main thinking region?

Explain natural vegetative propagation by roots in plants.

i. Draw two structural isomers of butane.
ii. Draw the structures of propanol and propanone.
iii. Name the third homologue of: a. alcohols
b. aldehydes
iv. Name the following:


v. Show the covalent bond formation in nitrogen molecule.

A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
(a) Draw a diagram to show this pattern of iron filings.
(b) Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines.
(c) How is the direction of magnetic field at a point determined using the field lines? Why do two magnetic field lines not cross each other?OR
How are the magnetic field lines of a bar magnet drawn using a small compass needle? Draw one magnetic field line each on both sides of the magnet.

Adrenaline is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart. As a result, the heart beats faster, resulting in the supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation. Such animal hormones are part of the endocrine
system which constitutes the second way of control and coordination in our body.



(a) How does chemical coordination take place in animals ?
(b) Which hormone is called an emergency hormone?
(c) Where are the adrenal gland present in our body?

OR

How does our body respond when adrenaline is secreted into the blood ?